1. Field of the Invention
The present invention relates to sealing of the heads of fasteners, such as nails, bolts, and the like, to the surrounding surface into which the fastener extends, to prevent the passage of liquids under the fastener head and along the fastener body. More particularly, the present invention relates to a sealant applicator tip structure and to a method of applying a resilient sealant compound over and around the head of a fastener to provide a fluid-tight seal between the fastener head and the surrounding surface.
2. Description of the Related Art
Flat headed fasteners, such as nails, screws, bolts, or the like, frequently work loose over time to cause the fastener head to be spaced from the surface of the material into which the fastener extends. For example, when roofing materials such as shingles, or other roofing materials is sheet form are applied by nailing the materials to a roof sub-surface, or to trusses or other structural members that support a roof, the periodic variation from the high temperatures of summer to the low temperatures of winter, and back to high temperatures again, as well as the temperature changes that occur over the course of a twenty-four hour period, can cause differential expansion and contraction of the roofing material and the underlying structural materials. The differential expansion and contraction tends to work loose the nails that were originally firmly driven into the underlying structure. Typically, the nails are pushed upwardly and outwardly from the nail hole, as a result of which the nail heads are separated from the surrounding surface and the nail holes become enlarged, leaving a gap so that rain can pass between the nail head and the surrounding surface, and can also pass between the nail shank and the nail hole to flow along the nail hole and along the loosened nail, and finally into the interior of the structure over which the roof extends. Other causes for nail loosening include earth and resulting foundation shifts and wind forces, all of which impose changing stresses on the structure, also tending to work the roofing nails loose. In addition to permitting rain leaks, the enlarged nail holes can become rotted after time, as a result of which the nails would no longer serve to securely hold the roofing material in place.
Various types of auxiliary connection arrangements have been proposed to overcome the separation and leakage problems of the type described above. For example, in U.S. Pat. No. 2,417,262, which issued on Mar. 11, 1947, to E. M. Morehouse, there is disclosed a sealing nut including a preformed, jacket-like outer member formed of rubber or other flexible material to provide a fluid-tight seal.
In U.S. Pat. No. 3,470,787, which issued on Oct. 7, 1969, to W. L. Mackie, there is disclosed a corrosion preventive device in the form of a dome-shaped cap defining a cavity that is filled with a sealing material, such as silicone rubber. A closure film is applied over the sealing material. In use, the closure film is removed from the cap, which is then manually pressed over the head of the fastener to prevent corrosion of the fastener head.
In U.S. Pat. No. 5,018,329, which issued on May 28, 1991, to S. Riaz Hasan et al., a roofing fastener is disclosed wherein a roofing washer is placed against the lower face o a nail head and a molded thermoplastic insert is positioned between the nail head and the washer. The thermoplastic insert is softened by heating to heat weld the parts together.
It is an object of the present invention to provide an improved sealing arrangement that does not require costly, separately formed molded parts, that permits sealing of new or existing fasteners quickly and without excessive labor, and that provides a long-lasting seal around a fastener head.